There are cases when a blob resource's backing might get detached
and re-attached again such as when the underlying object is getting
migrated in the Guest. In these situations, we need to obtain a new
dmabuf fd, which can be done by calling virtio_gpu_init_udmabuf().

Cc: Marc-André Lureau <marcandre.lureau@redhat.com>
Cc: Alex Bennée <alex.bennee@linaro.org>
Cc: Akihiko Odaki <odaki@rsg.ci.i.u-tokyo.ac.jp>
Cc: Dmitry Osipenko <dmitry.osipenko@collabora.com>
Signed-off-by: Vivek Kasireddy <vivek.kasireddy@intel.com>
---
 hw/display/virtio-gpu.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/hw/display/virtio-gpu.c b/hw/display/virtio-gpu.c
index 2f9133c3b6..1654a417b8 100644
--- a/hw/display/virtio-gpu.c
+++ b/hw/display/virtio-gpu.c
@@ -938,6 +938,10 @@ virtio_gpu_resource_attach_backing(VirtIOGPU *g,
         cmd->error = VIRTIO_GPU_RESP_ERR_UNSPEC;
         return;
     }
+
+    if (res->blob_size && res->dmabuf_fd < 0) {
+        virtio_gpu_init_udmabuf(res);
+    }
 }
 
 static void
-- 
2.50.1

On 2025/09/03 7:42, Vivek Kasireddy wrote:
> There are cases when a blob resource's backing might get detached
> and re-attached again such as when the underlying object is getting
> migrated in the Guest. In these situations, we need to obtain a new
> dmabuf fd, which can be done by calling virtio_gpu_init_udmabuf().

It sounds like a bug fix. Perhaps you may add a Fixes: tag and reorder 
patches to make this change come first.

> 
> Cc: Marc-André Lureau <marcandre.lureau@redhat.com>
> Cc: Alex Bennée <alex.bennee@linaro.org>
> Cc: Akihiko Odaki <odaki@rsg.ci.i.u-tokyo.ac.jp>
> Cc: Dmitry Osipenko <dmitry.osipenko@collabora.com>
> Signed-off-by: Vivek Kasireddy <vivek.kasireddy@intel.com>
> ---
>   hw/display/virtio-gpu.c | 4 ++++
>   1 file changed, 4 insertions(+)
> 
> diff --git a/hw/display/virtio-gpu.c b/hw/display/virtio-gpu.c
> index 2f9133c3b6..1654a417b8 100644
> --- a/hw/display/virtio-gpu.c
> +++ b/hw/display/virtio-gpu.c
> @@ -938,6 +938,10 @@ virtio_gpu_resource_attach_backing(VirtIOGPU *g,
>           cmd->error = VIRTIO_GPU_RESP_ERR_UNSPEC;
>           return;
>       }
> +
> +    if (res->blob_size && res->dmabuf_fd < 0) {
> +        virtio_gpu_init_udmabuf(res);
> +    }
>   }
>   
>   static void

> Subject: Re: [RFC 5/6] virtio-gpu: Recreate the resource's dmabuf if new
> backing is attached
> 
> On 2025/09/03 7:42, Vivek Kasireddy wrote:
> > There are cases when a blob resource's backing might get detached
> > and re-attached again such as when the underlying object is getting
> > migrated in the Guest. In these situations, we need to obtain a new
> > dmabuf fd, which can be done by calling virtio_gpu_init_udmabuf().
> 
> It sounds like a bug fix. Perhaps you may add a Fixes: tag and reorder
> patches to make this change come first.
Sure, I can do that.

Thanks,
Vivek

> 
> >
> > Cc: Marc-André Lureau <marcandre.lureau@redhat.com>
> > Cc: Alex Bennée <alex.bennee@linaro.org>
> > Cc: Akihiko Odaki <odaki@rsg.ci.i.u-tokyo.ac.jp>
> > Cc: Dmitry Osipenko <dmitry.osipenko@collabora.com>
> > Signed-off-by: Vivek Kasireddy <vivek.kasireddy@intel.com>
> > ---
> >   hw/display/virtio-gpu.c | 4 ++++
> >   1 file changed, 4 insertions(+)
> >
> > diff --git a/hw/display/virtio-gpu.c b/hw/display/virtio-gpu.c
> > index 2f9133c3b6..1654a417b8 100644
> > --- a/hw/display/virtio-gpu.c
> > +++ b/hw/display/virtio-gpu.c
> > @@ -938,6 +938,10 @@ virtio_gpu_resource_attach_backing(VirtIOGPU
> *g,
> >           cmd->error = VIRTIO_GPU_RESP_ERR_UNSPEC;
> >           return;
> >       }
> > +
> > +    if (res->blob_size && res->dmabuf_fd < 0) {
> > +        virtio_gpu_init_udmabuf(res);
> > +    }
> >   }
> >
> >   static void